Arvi Hakanen - Academia.edu (original) (raw)

Papers by Arvi Hakanen

Journal of Research in Science Teaching, Jan 4, 2019

An international collaborative investigation of beginning seventh grade students' understandings ... more An international collaborative investigation of beginning seventh grade students' understandings of scientific inquiry: Establishing a baseline.

Radiation Protection Dosimetry, Dec 15, 2007

A thermoluminescence dosemeter (TLD)-entrance surface dose (ESD) phantom combination was calibrat... more A thermoluminescence dosemeter (TLD)-entrance surface dose (ESD) phantom combination was calibrated in terms of air-kerma in IEC RQR X-ray radiation qualities between 50 and 150 kV. The ESD phantom was designed and constructed as a part of the work. With the combination, air-kermas were measured for four radiological examinations (two chest and two lumbar spine examinations in two hospitals), and converted to ESDa using Monte-Carlo calculated BSF data tabulated for different tube voltages, filtrations and beam diameters at 1 m distance. The results agreed with the ionisation-chamber measurements within the reported overall uncertainty of the TLD method. In the calibration, the ESD phantom can be replaced by the ISO water slab phantom unaffecting the reported overall uncertainty. Backscatter-related parameters for the ISO water slab phantom and the newly designed ESD phantom were determined for the IEC RQR qualities used in the secondary standard dosimetry laboratory of STUK at 1 m distance, including an approximate Hp(10)/Hp(0.07) ratio.

Analytica Chimica Acta, Aug 1, 1994

... A study of the terbium(II)-intermediate pathway of terbium(III) lyoluminescence continues in ... more ... A study of the terbium(II)-intermediate pathway of terbium(III) lyoluminescence continues in our laboratory and in this respect, some promising results has been obtained from ... Acknowledgement The assistance of Mr. Kai Rusi in the experimental work is gratefully acknowledged. ...

Instrumentation Science & Technology, 2002

In order to reach a dose rate of ca. 20 Gy/min with a typical Co radiotherapy unit, lactic acid b... more In order to reach a dose rate of ca. 20 Gy/min with a typical Co radiotherapy unit, lactic acid bacteria (LAB) are irradiated at a 20 cm source-to-specimen distance (SSD). By choosing an SSD which is a fourth part of the conventional 80 cm, the dose rate in the specimen is increased by a factor of ca. 16. A Monte Carlo simulation of the CGR Alcyon II Co radiotherapy unit at 20 cm SSD is performed using a BEAM-EGS4 Monte Carlo code. As a result of calculations, relative dose distributions in a solid-water phantom are shown, together with measured thermoluminescence dosimetry (TLD) data. An additional scattering component due to the sideways scattering from the beam limiting device structures of the radiotherapy unit is seen in the beginning of the BEAM data.

Radiation Protection Dosimetry, Jun 4, 2007

Characteristics necessary to specify an ISO 6980 Series 1 reference radiation field were determin... more Characteristics necessary to specify an ISO 6980 Series 1 reference radiation field were determined for a commercially available 85Kr beta-particle source, using a BEAM EGS4 Monte Carlo code. The characteristics include residual maximum beta energy, E(res), and the uniformity of the dose rate over the calibration area. The E(res) and the uniformity were also determined experimentally, using an extrapolation ionization chamber (EC) and a 0.2 cm3 parallel plate ionization chamber, respectively. The depth-dose curve measured with the EC gave a value 0.62 MeV for the E(res). Series 2 90Sr + 90Y and Series 1(85) Kr beta-particle sources calibrated for H(p)(0.07) at the secondary standard dosimetry laboratory (SSDL) of STUK were used to determine the energy and angular responses of DIS-1 direct ion storage dosemeters. The averaged zero angle H(p)(0.07) responses to the 90Sr + 90Y and 85Kr reference radiations were 135 and 80%, respectively. The responses were normalized to 100%, H(p)(0.07) response to 137Cs photon radiation.

Physics in Medicine and Biology, Jul 31, 2012

Drug Development and Industrial Pharmacy, 1995

AbstractAcoustic emissions were detected, both during the roller compaction of the microcrystalli... more AbstractAcoustic emissions were detected, both during the roller compaction of the microcrystalline cellulose powder and from single tablets after compaction by a single-punch tablet machine, via air using a microphone with a flat frequency response up to 20 kHz. Both of the compaction units were instrumented for the measurement of applied compressive force. The microcrystalline cellulose roller compacted using compressive forces below 30 kN showed a quite normal compaction behaviour but the product compacted at this force split into two and turned to yellow by its edges. This “capping” phenomenon was indicated by an enhancement of acoustic emission in the region of about 17-23 kHz. Acoustic emissions from single tablets after compaction by a single-punch tablet machine seemed to appear as wave packets consisting in very many frequency components that may, in addition, be time-varying. However, some small peaks were found probably being characteristic of these transient sounds.

Drug Development and Industrial Pharmacy, 1993

ABSTRACT Abstract Acoustic emission was detected during compaction of three different pharmaceuti... more ABSTRACT Abstract Acoustic emission was detected during compaction of three different pharmaceutical materials: lactose monohydrate, microcrystalline cellulose and maize starch varying compressive forces between 0 and 60 kN. Acoustic emission signals were recorded on magnetic tape with a microphone and transformed to frequency spectra by using FFT-analysis. After rough identification of frequency components each spectrum was divided into three bands. By using integrated band powers the acoustic activity on these bands could be compared quantitatively. Many frequency peaks were observed, too, and many of them could be identified.

Radiation Protection Dosimetry, Feb 20, 2009

137Cs sources are widely used in calibrations of radiation protection dosimeters and doserate met... more 137Cs sources are widely used in calibrations of radiation protection dosimeters and doserate meters. In these calibrations, conversion coefficients from the air kerma to various dose equivalent quantities are needed. These conversion quantities are functions of photon energy. In this work, Monte Carlo simulations and measurements are used for quantifying the energy distributions of the photon fluence from two 137Cs sources used for calibration purposes. The results indicate that the standard set of conversion coefficients, obtained from a monoenergetic spectrum, do not sufficiently take into account the scattered radiation (most of which is scattered by the source itself): For the large (14x15.6 mm) and small (3.5x3 mm) 137Cs sources, the simulated values for the conversion coefficients H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;(0.07)/Ka and H*(10)/Ka (which were nearly equal for the both quantities) showed around 1.0 and 1.5% deviations from the ISO standard value 1.20 (for the large and small sources, respectively). Similarly, the conversion coefficient Hp(10)/Ka showed around 1.5 and 2.5% deviations from the ISO standard value 1.21 for the large and small 137Cs sources, respectively, whereas Hp(0.07)/Ka had the values 1.22 and 1.23. The amplitude of the variation of the conversion coefficients due to varying 137Cs source size did not exceed 1%. Thus, the overall uncertainty (with coverage factor k=2) due to varying source size for the average values of the conversion coefficients can be estimated as low as 0.6%.

EPL, Jul 1, 1997

Photoluminescence spectra of thin-film aluminium oxide samples on aluminium show spectral lines a... more Photoluminescence spectra of thin-film aluminium oxide samples on aluminium show spectral lines at ca. 330 and 420 nm that are attributed to the F+ and F centers of aluminium oxide, respectively. Experimental results reveal that the F centers are responsible for the intrinsic cathodic luminescence of an oxide-covered aluminium electrode, too. The mechanism of the luminescence is based on charge

Medical Physics, Apr 15, 2004

A scintillation dosemeter is calibrated for 90 Sr/ 90 Y beta rays from an ophthalmic applicator, ... more A scintillation dosemeter is calibrated for 90 Sr/ 90 Y beta rays from an ophthalmic applicator, using an extrapolation ionization chamber as a reference instrument. The calibration factor for the scintillation dosemeter agrees with that given by the manufacturer of the dosemeter within ca. 2%. The estimated overall uncertainty of the present calibration is ca. 6% ͑2 sd͒. A calibrated beta-ray ophthalmic applicator can be used as a reference source for further calibrations performed in the laboratory or in the hospital.

Journal of Alloys and Compounds, Jul 1, 1995

Hydrated Tb(III) can be excited in aqueous solutions by various pathways during X-ray irradiation... more Hydrated Tb(III) can be excited in aqueous solutions by various pathways during X-ray irradiation. The dominating pathway is probably due to chemical excitation, induced by oxidation of Tb(III) by ionized water molecules, followed by immediate reduction of the resulting Tb(IV) to Tb(III) by hydrated electrons or atomic hydrogen. The high enthalpy of this reduction reaction produces Tb(III) in its highly excited states resulting in typical 5D4~TFI multiplet peak emissions. Other possible excitation pathways are direct excitation of Tb(III) by an impact of X-ray photons or photoelectrons, photoluminescent UV excitation due to the solid state emission of the cell materials, and/or an energy transfer from the excited water molecules. The same excitation mechanisms are also valid for chelated Tb(III), but the chelates with aromatic moieties produce luminescence predominantly by a sensitized mechanism where the aromatic moiety is first chemically excited by radical reactions, followed by an energy transfer to the central ion. Radiative relaxation of chelated Tb(III) results in an emission spectrum similar to that of hydrated Tb(III), but with a radioluminescence intensity considerably stronger than that of hydrated Tb(III).

Thermochimica Acta, 1995

... [2]. AA Badwan, H. Al-Kaysi, L. Owais, M. Sheikh-Salem and A. Arafat. In: K. Florey, Editor, ... more ... [2]. AA Badwan, H. Al-Kaysi, L. Owais, M. Sheikh-Salem and A. Arafat. In: K. Florey, Editor, Analytical Profiles of Drug Substances Vol. 19, Academic Press (1990), p. 627. Abstract | PDF (2203 K) | View Record in Scopus | Cited By in Scopus (10). ...

Journal of the Chemical Society, Faraday Transactions, 1996

ABSTRACT TbIII chelates containing aromatic moieties show sonoluminescence in aqueous solutions d... more ABSTRACT TbIII chelates containing aromatic moieties show sonoluminescence in aqueous solutions during the sonolysis of water. The observed 5D4→7FJ transitions of TbIII are due to the excitation of ligand, followed by an intramolecular energy transfer from the ligand to the central ion, which finally emits. No sonoluminescence of hydrated or EDTA-chelated TbIII ion could be observed. Ligand excitation can be based either on an energy transfer from the intrinsic emission centres of the sonolysis of water to the aromatic ligand, or on redox reactions between the ligand and hydroxyl radicals and hydrogen atoms produced by the sonolysis of water. Experimental results give greater support to the latter, chemiluminescent, excitation pathway.

Radiation Protection Dosimetry, Dec 16, 2006

The conversion coefficients from air kerma to ICRU operational dose equivalent quantities for STU... more The conversion coefficients from air kerma to ICRU operational dose equivalent quantities for STUK&amp;amp;amp;#39;s realisation of the X-radiation qualities N-15 to N-60 of the ISO narrow (N) spectrum series were determined by utilising X-ray spectrum measurements. The pulse-height spectra were measured using a planar high-purity germanium spectrometer and unfolded to fluence spectra using Monte Carlo generated data of the spectrometer response. To verify the measuring and unfolding method, the first and second half-value layers and the air kerma rate were calculated from the fluence spectra and compared with the values measured using an ionisation chamber. For each radiation quality, the spectrum was characterised by the parameters given in ISO 4037-1. The conversion coefficients from the air kerma to the ICRU operational quantities Hp(10), Hp(0.07), H&amp;amp;amp;#39;(0.07) and H*(10) were calculated using monoenergetic conversion coefficients at zero angle of incidence. The results are discussed with respect to ISO 4037-4, and compared with published results for low-energy X-ray spectra.

Journal of the Chemical Society, Faraday Transactions, 1997

ABSTRACT Light emission from aluminium oxide during cathodic pulse-polarisation of oxide-covered ... more ABSTRACT Light emission from aluminium oxide during cathodic pulse-polarisation of oxide-covered aluminium in aqueous solution was observed to be strongly enhanced in the presence of peroxydisulfate ions. The spectrum of the light emission had a broad maximum between 400 and 450 nm being attributed to F-centre luminescence of aluminium oxide. The mechanism of the luminescence is associated with the two-step reduction of peroxydisulfate anions near the oxide-covered cathode where the first one-electronic reduction step occurs either (i) by tunnel-emission generated hydrated electrons or (ii) by trickling down the surface states to the energy level of peroxydisulfate ion or (iii) by direct heterogeneous electron transfer from the bottom of the aluminium oxide conduction band to peroxydisulfate ions during strong downward band bending induced by cathodic pulse-polarisation. The second step occurs by electrons from F- or F + -centres at the oxide/electrolyte interface. Transitions of aluminium oxide conduction band electrons to fill the sulfate radical-emptied electron trapping sites (oxygen vacancies) produces analogous F- and F + -centre luminescence to that occurring during photoluminescence and thermoluminescence of aluminium oxide. No enhancement of light emission was observed in the presence of hydrogen peroxide which is also reduced in a two-step process at oxide-covered aluminium electrode. This can be explained by the fact that the energy level of hydroxyl radical under the present conditions lies ca. 1 eV above, whereas the energy level of sulfate radical lies somewhat below the colour-centre sub-band of aluminium oxide. Therefore, the sulfate radical is a sufficiently strong oxidant but the hydroxyl radical is too weak an oxidant to abstract electrons from F- and F + -centres.

Instrumentation Science & Technology, Apr 1, 1999

ABSTRACT Time-resolved detection utilizing a rotating chopper for x-rays allowed us die compariso... more ABSTRACT Time-resolved detection utilizing a rotating chopper for x-rays allowed us die comparison between soft x-ray irradiation-induced luminescences (RL) and photoluminescences (PL) of Tb aq complexed by chloride ion, sulfate ion, and different combinations of five aminopolycarboxylates. RL lifetimes and relative intensities of Tb aq were observed to increase with the number of coordinating groups of the aliphatic ligand analogously to the PL results. No deviation from the Horrocks-Sudnick behaviour was observed. Experimental results support the proposal that the aliphatic complexes of Tb aq are excited via direct action of radiation under soft x-ray irradiation.

Analytica Chimica Acta, Mar 1, 1999

Dissolution of X-ray irradiated sodium chloride or additively coloured potassium chloride induces... more Dissolution of X-ray irradiated sodium chloride or additively coloured potassium chloride induces generation of hydrated electrons which produce thallium(I)-specific chemiluminescence in the presence of thallium(I) ions. Such a luminescence is also called extrinsic lyoluminescence (ELL) of X-ray irradiation coloured sodium chloride, or additively coloured potassium chloride. The present ELL is considered chemiluminescence induced by dissolution-produced strong reducing and oxidising agents,

Journal of Alloys and Compounds, Jul 1, 1998

Energy transfer between aluminium oxide F-center and lanthanide cations at an oxide-covered alumi... more Energy transfer between aluminium oxide F-center and lanthanide cations at an oxide-covered aluminium electrode during the cathodic III pulse-polarization of the electrode is investigated by means of Stern-Volmer luminescence quenching kinetics. Terbium-specific extrinsic luminescence is observed while some other lanthanides are observed to quench the F-center luminescence. Different quenching efficiencies of the lanthanides are discussed to be dependent on the different energy acceptor characteristics of the tri-or divalent lanthanides.